Continuous monitoring of vital signs with the ability to remotely monitor patient status is a growing field and the ability to incorporate multiple measurement capabilities into a single small unobtrusive patch that can be worn by a patient (i.e., a body worn patch) for multiple days at a time is a desirable feature. One such measurement is blood oxygen concentration, often carried out by a pulse oximeter. However, current pulse oximeter designs are not conducive to being powered by an ultra-low power source, such as a small coin cell battery, and thus not suited for incorporation into a body worn patch.